Objects or components may be formed by forging. By way of example, FIG. 1(a) shows a gas turbine combustion chamber casing 10, which may be manufactured from a large single piece forging 20. (FIG. 1 shows sections through the combustion chamber casing 10, which is substantially tubular with a longitudinal axis 30.) The design of such casings 10 dictates the envelope of the forging 20. The forging may then be machined to provide the finished product. However, it is typical that approximately 90% of the purchased material has to be removed to produce the finished component. Consequently, the current method of manufacture of gas turbine combustion chamber casings results in a material ‘fly to buy’ ratio of approximately 10%. Whilst this excess material may be recycled, it does not command the same scrap price as the purchase price. This incurs cost in both cycle time to remove the material and consumables.
Alternatively, Hot Isostatic Pressing (HIP), for example powder HIP, may be used as a method of manufacture, as it may have a much better ‘fly to buy’ ratio. As shown in FIG. 1(b), powder HIP requires a tool 40, e.g. a mould, to be manufactured from a large forging. The tool 40 may comprise a plurality of portions 40a-c, which may be separated to remove the casing 10. However, any external features on the object or component being moulded need to be machined on the inside of the mould, which causes access problems for both machining and inspection. Furthermore, the machining of internal features deep inside a mould requires the use of long tooling and right angled heads that are not as rigid as standard tooling. This can result in tool ‘push off’ and tool chatter resulting in non-conforming features on the mould. As a result, machining with such tools is generally quite slow and expensive. In addition, if any of the internal features are machined incorrectly then the mould could be scrap.
The present invention therefore seeks to address these issues.